Possible fungus on lavender plants - Ask Extension
Hello,
I live in Marcola, Oregon and I have been battling a problem with my lavender plants. I think it may be blight , but I wanted to send some ph...
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Possible fungus on lavender plants #912784
Asked August 05, 2025, 2:22 PM EDT
Hello,
I live in Marcola, Oregon and I have been battling a problem with my lavender plants. I think it may be blight , but I wanted to send some photos to you and to see if you could help. My lavender plants are about 2 years old and this spring I noticed tiny black dots all over the inside foliage of the plant. It is still growing well and the outside leaves are not affected yet. The plants are quite dense. In the second photo I am holding a piece of sticky, seemingly like spider web material. That was on the underneath of the plant. Then I noticed when I shook the plant, that little fruit fly sized bugs would fly out. I got lucky and was able to catch one. Those are the photos at the end. Thank you for any help you can provide! Oh, and my plants are a type of Spanish lavender. I guess sometimes it is called topped lavender. I also sent this question to an email address I found here. Just thought I would leave this here as well.
-Sarah
Lane CountyOregon
Expert Response
Whiteflies are tiny, sap-sucking insects that may become abundant in vegetable and ornamental plantings, especially during warm weather. They excrete sticky honeydew and cause yellowing or death of leaves. Outbreaks often occur when the natural biological control is disrupted. Whiteflies normally lay their tiny oblong eggs on the undersides of leaves. The eggs hatch, and the young whiteflies gradually increase in size through four nymphal stages called instars. The first nymphal stage (crawler) is barely visible even with a hand lens. The crawlers move around for several hours before settling to begin feeding. Later nymphal stages are immobile, oval, and flattened, with greatly reduced legs and antennae. All stages feed by sucking plant juices from leaves and excreting excess liquid as drops of sticky honeydew as they feed. Leaves may be sticky or covered with black sooty mold that grows on honeydew. Management is difficult once populations are high.
whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves or hosing down with water sprays. Reflective mulches can repel whiteflies from vegetable gardens, and yellow sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. Whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves or hosing down with water sprays. Reflective mulches can repel whiteflies from vegetable gardens, and yellow sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. If these descriptions do not seem to fit what you feel on the plants, please get back to me with a clearer picture of the insect.